Radiotelephony network with multi-carrier packet data transmission

ABSTRACT

The present invention relates to a radio telephony network supporting at least one link of a radio channel for a packet data transmission service. The radio telephony network comprises a plurality of network controllers (RNC). Each network controller (RNC) is connected, via an interface I ub , to at least one base radio station (B-node) supervising at least one macrocell. The radio telephony network additionally comprises at least one base radio microstation (B1-micronode) connected to the network controller (RNC) via an interface I ub  of the same type as that connecting the base radio station (B-node) to said controller. The base radio microstation (B1-micronode) supervises at least one microcell incorporated in at least one macrocell. The base radio microstation (B1-micronode) provides the packet data transmission service in the microcell on the link of the radio channel, preferably using multicarrier radio access. The multi-carrier radio access is preferably of the OFDM type.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.10/553,951, filed Oct. 21, 2005, now U.S. Pat. No. 7,835,318, which is anational phase application based on PCT/IB2003/001502, filed Apr. 23,2003, each of which is incorporated herein by reference in its entirety.

The present invention relates generally to the field of radio telephonyand particularly to a radio telephony network, for example a thirdgeneration radio telephony network. More particularly, the presentinvention relates to a third generation radio telephony network withpacket data transmission provided by a multi-carrier technique such asOFDM (“Orthogonal Frequency Division Multiplexing”).

Known radio telephony systems such as GSM are essentially intended forvoice communication. They use two symmetrical links, namely a downlink(from a terrestrial base station to a mobile station) and an uplink(from a mobile station to a base station).

The systems under development are also based on a structure of thistype. Thus, the UMTS standard issued by ETSI provides for twosymmetrical links, one for uplink and one for downlink.

One of the problems to be faced by radio telephony in the forthcomingyears is the presence of new services and new applications requiringvery high speed data transmission.

Recent studies have shown that the resources allocated to thetransmission of data (files, sounds, fixed or animated images),particularly via Internet or other similar networks, will form thepredominant part of the resources available from the year 2005 onwards,while the resources allocated to voice communication are expected toremain practically constant.

WO 99/53644 describes the transmission of a cellular radio telephonesignal via a symmetrical two-way main channel, including a main uplinkand a main downlink, in particular for data transmission at medium orlow speed and for the transmission of signaling information and controldata, and comprising at least one additional channel assigned solely tothe downlink for high-speed data transmission.

The main channel uses a code division access method (CDMA), while thesupplementary channel uses a multi-carrier technique.

The multi-carrier technique is implemented by the simultaneoustransmission of carrier frequencies (using the OFDM technique forexample).

In particular, said supplementary channel uses the “IOTA” modulationtechnique.

Additionally, the document R1-02-1222, Reference OFDM Physical LayerConfiguration, Nortel Network, 3GPP TSG RAN1 Meeting#28bis, Espoo,Finland, Oct. 8-9, 2002 (associated slides R1-02-22) describes anexample reference OFDM configuration which may be considered to evaluatethe performance of OFDM in the framework of the SI (“Study Item”) onOFDM introduction in UTRAN. This OFDM configuration assumes the use of aseparate downlink carrier bearing an OFDM HS-DSCH (High Speed-DownlinkShared Channel) transmission or an OFDM DSCH (Downlink Shared Channel)transmission.

The Applicant faced the problem of making a radio telephony networkcapable of providing a high-speed packet data transmission service inareas where high traffic is expected.

The Applicant has observed that the problem described above can besolved with a radio telephony network supporting at least one link of aradio channel for a packet data transmission service. The radiotelephony network comprises a plurality of network controllers RNC, eachconnected via an I_(ub) interface to at least one base radio stationsupervising at least one macrocell. The radio telephony network alsocomprises at least one base radio microstation, connected to the networkcontroller via an I_(ub) interface of the same type as that connectingthe base radio station to the network controller RNC. Each base radiomicrostation supervises one or more microcells 5 b incorporated in atleast one macrocell served by the base radio station. The microcells arecentered at points different from the center of the macrocell, where the“center of the macrocell” denotes the point at which the base radiostation is located. The microcells correspond to areas where hightraffic is expected (known as “hot spots”), such as airports, stadium,small urban centers, hotels, commercial centers etc. (outdoorenvironments) or buildings etc. (indoor office environments) in whichthe base radio microstations provide the packet data transmissionservice via the link of the radio channel, preferably usingmulti-carrier radio access. The multi-carrier radio access is preferablyof the OFDM type. The link of the radio channel is preferably thedownlink.

According to the present invention, it is therefore provided a radiotelephony network supporting at least one link of a radio channel for apacket data transmission service. The radio telephony network comprisesa plurality of network controllers RNC, each network controller RNCbeing connected, via an I_(ub) interface, to at least one base radiostation supervising at least one macrocell. The radio telephony networkis characterized in that it additionally comprises at least one baseradio microstation, connected to the network controller RNC via anI_(ub) interface of the same type as that connecting the base radiostation to the network controller RNC. The base radio microstationsupervises at least one microcell incorporated in at least onemacrocell. This microcell is centered at a point different from thepoint at which the macrocell is centered. The base radio microstationprovides said packet data transmission service via at least one link ofthe radio channel.

In particular, the base radio microstation provides the packet datatransmission service by means of a multi-carrier radio access. Saidmulti-carrier radio access is preferably of the OFDM type. Said link ofthe radio channel is preferably the downlink.

According to another aspect of the present invention, each base radiomicrostation comprises a central switch and a plurality of access portsconnected to said central switch by a cable.

Specifically, each base radio microstation comprises a protocolstructure including a first protocol level and a second protocol levellocated above said first protocol level, said first protocol level L1being a physical level and said second protocol level L2 being a datatransmission level.

The first protocol level L1 includes circuit components for processing amulti-carrier radio signal formed by a plurality of radio carriersassociated with data to be transmitted. Said circuit components forprocessing said multi-carrier radio signal comprise dedicated circuitsand/or programmable DSPs.

The data transmission level comprises an access control sub-level MACincluding an entity MAC-OFDM for controlling said multi-carrier radioaccess. The logical entity MAC-OFDM maps logical channels on thetransport channels, implements functions of retransmission ofincorrectly received data packets, and implements scheduling functions.

The access control sub-level MAC of each base radio microstation alsocomprises a frame protocol OFDM-FP for controlling the transport of themulti-carrier radio signal between the base radio microstation and thenetwork controller RNC connected to it.

Advantageously, the central switch comprises the logical entity MAC-OFDMand the frame protocol OFDM-FP, in which each of the access ports APcomprises said first protocol level including said circuit componentsfor processing said one multi-carrier radio Signal.

Additionally, each network controller RNC comprises an access controlsub-level MAC including a frame protocol OFDM-FP for controlling thetransport of the multi-carrier radio signal within said networkcontroller RNC or between said network controller RNC and the base radiomicrostation connected to it.

Furthermore, the base radio microstation can provide said packet datatransmission service to at least one user equipment UE located in themicrocell served by the base radio microstation.

Advantageously, the user equipment UE comprises a protocol structureincluding a physical level comprising circuit components fordemodulating the multi-carrier radio signal.

The characteristics and advantages of the present invention will be madeclear by the following description of an example of embodiment providedfor guidance and without restrictive intent, with reference to theattached drawings, in which:

FIG. 1 is a schematic representation of a radio telephony networkaccording to the invention;

FIG. 2 shows a distribution of base radio microstations of the radiotelephony network of FIG. 1; and

FIG. 3 is a schematic representation of a protocol structure of aportion of the radio telephony network of FIG. 1.

FIG. 1 shows a third-generation radio telephony network 1, madeaccording to the invention. The radio telephony network 1 has a mainradio access of the CDMA type on a main radio channel 2 comprising twosymmetrical links, namely a main uplink 3 (uplink) and a main downlink 4(downlink), both, for example, with a 5 MHz bandwidth. The radiotelephony network 1 also supports a multi-carrier radio access on atleast one link of a supplementary radio channel 6 to provide a packetdata transmission service.

The supplementary radio channel 6, for example with a 5 MHz bandwidth,can be located within the radio frequency band assigned tothird-generation systems. These radio frequencies form a “core” band of230 MHz in the 1885÷2025 MHz and 2210÷2200 MHz portions of the spectrum.Alternatively, the supplementary radio channel 6 could be located in anextension of the aforesaid band. In this case, the 800÷960 MHz,1700÷1885 MHz and 2500÷2690 MHz portions of the spectrum, for example,have been identified.

The radio telephony network 1 comprises the following logical entities:

Core Network CN;

radio access network UTRAN (UMTS Terrestrial Radio Access Network);

user equipment UE.

More specifically, the Core Network CN, made according to the 3GPPspecifications, is a switching and routing infrastructureinterconnecting the various sections of the radio access network UTRANwhich, in turn, directly collects the traffic from a plurality of baseradio stations, referred to below as B-nodes, connected to the userequipment UE (for example cell phones, vehicles, electronic computers,etc.) via the main radio channel 2.

As shown in FIG. 1, the radio access network UTRAN is delimited by twointerfaces, namely a radio interface called U_(u) delimiting the radioaccess network UTRAN towards the user equipment UE and a networkinterface I_(u) connecting the radio access network UTRAN to the CoreNetwork CN.

In detail, the radio access network UTRAN comprises a plurality of radiosub-systems RNS (Radio Network System) connected to the Core Network CNvia the network interface I_(u). Each radio sub-system RNS includes anetwork controller RNC (Radio Network Controller) representing theboundary between the radio portion and the remaining network, and one ormore B-nodes, connected to the network controller RNC via an interfaceI_(ub). Each B-node, made according to the 3GPP specifications,supervises one or more macrocells 5 a, as shown in FIG. 2. Additionally,the network controllers RNC can be interconnected by means of aninterface I_(ur).

With reference to FIGS. 1 and 2, according to the invention, the radiotelephony network 1 also comprises one or more base radio microstations,referred to below as B1-micronodes, connected to the network controllersRNC via an interface I_(ub) of the same type as that connecting theB-nodes to the corresponding network controllers RNC. Each B1-micronodesupervises one or more microcells 5 b comprised in at least onemacrocell 5 a served by the B-node. The microcells 5 b are centred atpoints different from the center of the macrocell 5 a, where the “centerof the macrocell 5 a” denotes the point at which the base radio station(B-node) is located. In particular, the microcells 5 b correspond toareas where high traffic is expected (known as “hot spots”), such asairports, stadium, small urban centers, hotels, commercial centers etc.(outdoor environments) or buildings etc. (indoor office environments) inwhich the B1-micronodes provide the packet data transmission service.The B1-micronodes support at least one link of the supplementary radiochannel 6 for the packet data transmission service, using amulti-carrier radio access, preferably of the OFDM type.

Preferably, in indoor office environments characterized by confinedspaces, each B1-micronode can be made by a central switch SW, connectedto the corresponding network controller RNC, and a plurality of accessports AP connected to the central switch SW by a cable C_(v) which alsosupplies the power.

Functionally, each network controller RNC controls the radio resourcesand controls the radio transport, while each B-node/B1-micronode has thetask of implementing the radio transmission (modulation, reception andtransmission, power control) for carrying the information to the userequipment UE which is located in the macrocells 5 a/microcells 5 b.

In practice, each B-node/B1-micronode receives from the networkcontroller RNC connected to it the resources to send to the userequipments UE and transmits them over the air, adjusting their powerlevels according to information received from said network controllerRNC. At the same time, the B-node/B1-micronode carries out power andquality measurements on user equipment UE received signals for enablingthe network controller RNC to adjust its parameters in the management ofthe radio resources.

In particular, the B1-micronodes also have specific functions relatingto the protocol levels MAC and RLC which are described in detail in theremainder of the present description.

The system described above enables the user equipment UE to receiveservices supplied by the radio telephony network 1 even if they aresupplied by B-nodes/B1-micronodes belonging to network controllers RNCother than the original network controller of the call. This enables themobility of the user equipment UE to be managed efficiently by thenetwork controllers RNC.

In particular, the packet data transmission provided by theB1-micronodes in the microcells 5 b can reach a speed of 3÷24 Mb/s, forexample, depending on the type of modulation and signal coding used.Thus the user equipments UE located within the microcells 5 b canaccess, for example, Internet or other similar networks by directlyusing the radio telephony network 1, the B1-micronodes being connecteddirectly to the network controllers RNC.

To allow access to this functionality, the user equipment UE supportsboth CDMA radio access and multi-carrier radio access. This is becausethe request of the packet data transmission service and both theallocation of the radio resources and the dialog with the uplink 3 inthe call establishment phase and during the course of the service, takeplace by means of the CDMA radio access.

FIG. 3 shows schematically the protocol structure of a portion 7 of theradio telephony network 1 supporting, on a downlink of the supplementarychannel 6, the packet data transmission providing by means of amulti-carrier technique, preferably of the OFDM type. Specifically, inthe multi-carrier technique the data are transmitted by means of radiosignals comprising a plurality of carrier frequencies transmittedsimultaneously.

The radio telephony network 1 also has a conventional protocol structurefor reception and transmission according to the main CDMA radio access.

The network portion 7 comprises the user equipment UE protocols, theradio interface U, the B1-micronode protocols, the interface I_(ub), thenetwork controller RNC protocols and the interface I_(ur).

FIG. 3 also shows two different operating modes of the networkcontroller RNC, called Controlling RNC (C RNC) and Serving RNC (S RNC)respectively, as specified in 3GPP.

In particular, in the “controlling” mode the network controller RNCcontrols the traffic and the congestion situations of its own cells andterminates the interface I_(ub), while in the “serving” mode the networkcontroller RNC controls and manages the resources of the user equipmentUE and terminates the interface I_(u).

As shown in FIG. 3, the protocol structure of the network portion 7includes the first two levels of the OSI (Open System Interconnection)protocol stack, namely:

the physical level L1;

the data transmission level L2 (Data Link).

Additionally, the data transmission level L2 is divided into twosub-levels, namely an access control sub-level MAC (Medium AccessControl) and a transmission control sub-level RLC (Radio Link Control).

In particular, the physical level L1 offers services to the accesscontrol sub-level MAC in the form of transport channels.

The access control sub-level MAC controls the simultaneous accesses of aplurality of user equipments UE (multiple access) to the available radioresources, and offers services to the transmission control sub-level RLCvia logical channels characterized by the type of data transmitted.

The transmission control sub-level RLC controls the transmission of theinformation within the access network UTRAN, also offering aretransmission service for those packets which the physical level L1 hasbeen unable to deliver successfully to their destinations.

With further reference to FIG. 3, the user equipment UE comprises, fromthe bottom to the top, the physical level UE-L1-OFDM comprising circuitcomponents for demodulating a multi-carrier radio signal, preferably ofthe OFDM type; the access control sub-level MAC; and the transmissioncontrol sub-level RLC.

The B1-micronode comprises, from the bottom to the top, the physicallevel L1 and the access control sub-level MAC.

In greater detail, the physical level L1 of the B1-micronode next to theradio interface U_(u) comprises a portion B1-L1-OFDM made from circuitcomponents, such as dedicated circuits and/or programmable DSPs, whichcan process the multi-carrier radio signal, preferably of the OFDM type(channel coding, interleaving, transmission speed adaptation,modulation). The access control sub-level MAC includes the logicalentity B1-MAC-OFDM, located above the portion B1-L1-OFDM and below alogical entity MAC-c/sh present in the network controller RNC operatingin “controlling” mode. The logical entity MAC-c/sh of the networkcontroller RNC controls the common and shared channels, while thelogical entity B1-MAC-OFDM of the B1-micronode controls themulti-carrier radio access, preferably of the OFDM type. In particular,the logical entity B1-MAC-OFDM maps the logical channels on thetransport channels and also implements functions of a HARQ (HybridAutomatic Repeat Request) protocol and functions of scheduling (aprocedure which attempts to transmit only to the user equipment UEhaving favorable radio conditions). Specifically, the HARQ protocolcontrols the rapid request for retransmission of data packets which havenot been correctly received, and also makes use of the informationsupplied by the incorrect data packets in order to achieve a correctdecoding of said packets.

Additionally, the implementation of the scheduling functions within theB1-micronode provides greater efficiency in the execution of thisprocedure. This is because the scheduler can adapt the type ofmodulation to the conditions of the radio channel, transmitting only tothe user equipment UE for which the radio conditions are good, andallocating the radio resources of the radio telephony network 1 withappropriate algorithms.

Advantageously, the introduction of the logical entity B1-MAC-OFDMenables the mobile operator to provide packet data transmission,preferably using the OFDM technique, without modifying the higher levelsand protocols of the radio telephony network 1 (the transmission controlsub-level RLC and the protocol PCDP-Packet Data Convergence, the latterbeing present in the network level, or level L3, of the radio telephonynetwork 1).

Furthermore, the logical entity B1-MAC-OFDM enables the transmissioncontrol sub-level RLC to operate either in AM mode (OFDM transmissionfound) or in UM mode (OFDM transmission not found), and enables theprotocol PDCP to be configured for header compression, if required.

Next to the interface I_(ub), the access control sub-level MAC comprisesa frame protocol B1-OFDM-FP controlling the transport of data betweenthe B1-micronode and the network controller RNC connected to it.

If the B1-micronode is made by the central switch SW and the accessports AP, the central switch SW comprises the access control sub-levelMAC, including the logical entity B1-MAC-OFDM located next to the radiointerface U_(u), and the frame protocol B1-OFDM-FP located next to theinterface I_(ub). Each of the access ports AP comprises the physicallevel L1 including the portion B1-L1-OFDM comprising the logic requiredfor controlling the radio communication. In this way, practically allthe computing capacity is moved into the central switch SW, thusminimizing the space occupied by the access ports AP.

With further reference to FIG. 3, the network controller RNC comprises,from the bottom to the top, the physical level L1 and the datatransmission level L2.

In particular, in “controlling” mode the network controller RNCcomprises, from the bottom to the top, the physical level L1 and theaccess control sub-level MAC. The access control sub-level MAC comprisesthe frame protocol CRNC-OFDM-FP which, on the side facing the interfaceI_(ub) is located below the logical entity MAC-c/sh by the frameprotocol B1-OFDM-FP of the B1-micronode, and which, on the side facingthe interface I_(ur), is located below a logical entity MAC-d present inthe network controller RNC operating in “serving” mode. The logicalentity MAC-d has the task of controlling the dedicated channels.

In “serving” mode, the network controller RNC comprises, from the bottomto the top, the physical level L1, the access control sub-level MAC andthe transmission control sub-level RLC. The access control sub-level MACcomprises the frame protocol SRNC-OFDM-FP locating below the logicalentity MAC-d by the frame protocol CRNC-OFDM-FP of the networkcontroller RNC operating in “controlling” mode.

The frame protocol SRNC-OFDM-FP permits data transport within thenetwork controller RNC (if the interface I_(ur) is present) and directdialog between the B1-micronode and the network controller RNC operatingin “serving” mode (if the interface I_(ur) is not present).

Functionally, a data packet entering the network controller RNCoperating in “serving” mode is received by the transmission controlsub-level RLC and, subsequently, by the logical entity MAC-d, and thenenters the frame protocol SRNC-OFDM-FP and finally reaches B1-micronodevia the frame protocol CRNC-OFDM-FP of the network controller RNCoperating in “controlling” mode.

In the B1-micronode, the data packet passes through the frame protocolB1-OFDM-FP and is received by the logical entity B1-MAC-OFDM andsubsequently by the physical level B1-L1-OFDM.

The data packet then passes through the radio interface U_(u) and isreceived by the physical level UE-L1-OFDM of the user equipment UE andsubsequently by the access control sub-level MAC and by the transmissioncontrol sub-level RLC, and then becomes visible to the user.

Advantageously, in the radio telephony network 1 according to theinvention the updating of the B-nodes can also be provided, so thatthese nodes can support multi-carrier radio access, preferably of theOFDM type, on at least one link of the supplementary radio channel 6 toprovide the packet data transmission service.

In general, each B-node has a protocol structure comprising the physicallevel L1 and the access control sub-level MAC.

In the updated B-node, in order to provide the packet data transmissionservice in a downlink of the supplementary channel 6, the physical levelL1 comprises a portion B-L1-OFDM including circuit components, such asdedicated circuits and/or programmable DSPs capable of processing amulti-carrier radio signal; preferably of the OFDM type, while theaccess control sub-level MAC comprises the logical entity B-MAC-OFDMwhich is identical to the logical entity B1-MAC-OFDM describedpreviously.

The advantages of the radio telephony network 1 according to theinvention are evident from the above description. In particular, it ispointed out that this network can provide new business opportunities forthe mobile operator in so-called “hot spots”, since it is competitivewith WLAN networks both in terms of the bit rate obtainable and in termsof ease of deployment; in the latter case, the B1-micronodes B1 arepreferably made by the central switch SW and the access ports AP.

Additionally, if the radio telephony network 1 comprises both theupdated B-nodes and the B1-micronodes it can offer the user the mobilityfunctionalities provided by the radio sub-systems RNS; conversely, WLANnetworks cannot offer this basic functionality.

The applicant has also observed that the above description relating tothe downlink of the supplementary radio channel 6 can also be extendedto an uplink of said radio channel. This is because the B1-micronode B1made according to the present invention can be modified according to theteachings of the present invention to make it suitable for receiving andcontrolling any data packets transmitted by user equipment UE. Also inthis case, the radio access can be of the multi-carrier type, preferablyof the OFDM type.

The invention claimed is:
 1. A network node for providing a packet datatransmission service in a network, the network comprising at least onemacrocell and at least one microcell located within the at least onemacrocell, the network node comprising: circuitry configured toimplement a first set of protocol levels for transmitting packet data toa user equipment according to a first type of radio access used in theat least one macrocell; and circuitry configured to implement a secondset of protocol levels for transmitting packet data to the userequipment according to a multi-carrier radio access used in the at leastone microcell, the second set of protocol levels including a physicallevel and at least one protocol level located above the physical levelfor controlling the multi-carrier radio access, wherein the physicallevel includes a portion comprising at least one of dedicated circuitsand programmable digital signal processors (DSPs) configured to processa multi-carrier radio signal.
 2. The network node as claimed in claim 1,wherein the network node is a base radio station.
 3. The network node asclaimed in claim 1, wherein the first type of radio access is CDMA radioaccess.
 4. The network node as claimed in claim 1, wherein themulti-carrier radio access is OFDM radio access.
 5. The network node asclaimed in claim 1, wherein the at least one protocol level locatedabove the physical level for controlling the multi-carrier radio accessis an access control sub-level comprising a logical entity forcontrolling the multi-carrier radio access.
 6. The network node asclaimed in claim 1, wherein the second set of protocol levels providespacket data transmission without modifying the first set of protocollevels.
 7. The network node as claimed in claim 1, wherein the networknode is updated to configure circuitry in the network node to implementthe second set of protocol levels for transmitting packet data accordingto the multi-carrier radio access.
 8. The network node as claimed inclaim 1, further comprising circuitry configured to communicate with anetwork controller in the at least one macrocell.
 9. A method forproviding a packet data transmission service at a network node in anetwork, the network comprising at least one macrocell and at least onemicrocell located within the at least one macrocell, the methodcomprising: implementing a first set of protocol levels for transmittingpacket data to a user equipment according to a first type of radioaccess used in the at least one macrocell; and implementing a second setof protocol levels for transmitting packet data to the user equipmentaccording to a multi-carrier radio access used in the at least onemicrocell, the second set of protocol levels including a physical leveland at least one protocol level located above the physical level forcontrolling the multi-carrier radio access, wherein the physical levelincludes a portion comprising at least one of dedicated circuits andprogrammable digital signal processors (DSPs) configured to process amulti-carrier radio signal.
 10. The method as claimed in claim 9,wherein the network node is a base radio station.
 11. The method asclaimed in claim 9, wherein the first type of radio access is CDMA radioaccess.
 12. The method as claimed in claim 9, wherein the multi-carrierradio access is OFDM radio access.
 13. The method as claimed in claim 9,wherein the at least one protocol level located above the physical levelfor controlling the multi-carrier radio access is an access controlsub-level comprising a logical entity for controlling the multi-carrierradio access.
 14. The method as claimed in claim 9, wherein the secondset of protocol levels provides packet data transmission withoutmodifying the first set of protocol levels.
 15. The method as claimed inclaim 9, further comprising a step of updating the network node toimplement the second set of protocol levels for transmitting packet dataaccording to the multi-carrier radio access.